This invention relates to compositions for controlling many varieties of insects which are harmful to agricultural and ornamental crops. The compositions contain an inert diluent and an effective amount of certain tetraorganotin compounds which exhibit excellent and unexpected activity when compared to closely related trimethyl tetraorganotin compounds. In addition, the compounds exhibit reduced levels of phytotoxicity compared to trimethyltin compounds disclosed in the prior art.
The biological activity of compounds containing 3 hydrocarbon radicals bonded to a tin atom is well known. U.S. Pat. No. 3,264,177 discloses that tricyclohexyltin compounds effectively control arachnids, particularly spider mites, however these compounds are generally ineffective as insecticides. The use of certain trialkyltin compounds, including bis(trimethyltin)oxide and trimethyltin chloride as insecticides is disclosed in U.S. Pat. No. 3,702,360. While these trialkyltin compounds effectively control insects, their high phytotoxicity makes them impractical for commercial use.
Compounds containing 4 hydrocarbon groups bonded to a tin atom have for a long period of time been considered to possess, at best, only slight biological activity. In a text entitled "Chemistry of Organotin Compounds" R. C. Poller states that insecticidal activity is largely confined to compounds with three Sn-C bonds. He further states that variations in the nature of the fourth group attached to tin do not produce any striking effects. Despite this general statement a number of organotin compounds wherein the tin atom is bonded to three non-substituted hydrocarbon groups and a fourth hydrocarbon group containing a functional group, which often contains sulfur, have been disclosed as being effective insecticides. Patents claiming this type of organotin compound are discussed in detail in a subsequent portion of this specification.
It is an objective of this invention to provide organotin compound exhibiting insecticidal activity equivalent to trimethyltin compounds but with reduced levels of phytotoxicity, thereby making possible application of compositions containing these compounds to living plants.